148 PRACTICAL TREE REPAIR 



on as an additional protection and because black 

 is probably the best color for fillings. Many 

 workmen apply slaters' cement to the wood 

 just inside the mouth of the cavity, with the idea 

 of filling in advance the crack which always forms 

 between the concrete and the wood. I have not 

 found that method very successful, but I often ap- 

 ply the slaters' cement rather thickly to the region 

 of the crack after the filling has dried out. 



FILLING WITH ASPHALT 



There are many ways in which asphalt can be 

 used for filling trees. Invariably, however, it is 

 mixed with a cheaper material, being used as a 

 cement rather than as a homogeneous filling. The 

 materials thus cemented together may be sand, 

 sawdust, or excelsior. 



Mixed with sand, as it is in paving, it cannot 

 readily be built up and sur- 

 faced, so that if sand is used 

 as an aggregate the cavity 

 must be given a front wall 

 of sheet metal to act as a 

 Section of cavity filled dam while the mixture is be- 



with a metal-front • , • j . . • 



asphalt filling '"S P"* "1 ^nd as a protection 



to the surface after the job 



is done. If this method is used a shallow ledge 



must be cut along each side of the cavity, as for 



ordinary tinning. A sheet of zinc is then cut to 



